Process for reactivating clay



Aug. 23, 1932.

vE. R. LEpI-:RER PROCESS FOR REACTNATVIQNYG vCLAY- v.Filed may 51,19so` f @gamas-sheet 1 Y @wx QN. MW.

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. INVENTOR E/Qw//v RE 2E@ Aug'. 23, 1932. E. R. LEDERER PRocEss Fon REACTIvAT'ING CLAY 2 Sheets-Sheet 2 Filed May 31 1950 ...lll 5.x'.

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lPatented ug. 23, 1932 UNITED sTATEs PATENT oEFlcE Eawm a. LEnnnEn, or roar wonrn, 'rms Pnocnss ron nmcrrvarme CLAY Application led Hay 31,

bring about a substantial economy in the use of the clays by permitting repeated re-use thereof. Y

Another object of my invention is to provide a method and apparatus for' the treat-' ment and reconditioning of vdecolorizin clays whereby the efficiency of the origina clay is not materially reduced by repeated reconditioning treatments.

Another object of my invention-is to provide an apparatus and process for the treat- .2 ment'of finely ground clay usedin contact .filtration whereby the Yclay maybe recondi-` tioned for re-use from ten to twenty times before losing materially 'in its decolorizing eli'iciency'and whereby a greater'percentage 5 of the lubricating stock remaining` in the clay lter cake maybe saved than isvnormally possible.

Further objects and advantages of my invention will appear from the following de- 0 scription of preferred forms of embodiment 1 thereof in conjunction with the attached drawings which schematically illustrate the process, in `which: Y

Figure 1 is a schematic layout of one form process and treatment apparatus for the treatment ofthe clay. p 1

vFigure 2 is a view similar to Figure 1 but of a modified ,form of apparatus.

In the .treatment of lubricating oil stock 40, to Vremove decolorizing impurities,'wax and other solids therefrom it has become .customary to subject the oil which may or mayvnot have been previously treated with sulfurlc or other acid to the action of a decolorizing and bleaching clay such as montmorillonites,

' bentonites, etc., by intimately mixing the inely ground clay with the oil and then passing the mixture through a filter to separate the clay and sludge from the oil. Decolorizing and filtering c ays of the type commonly used 1930., Serial No. 457,688.

are fairly expensive and are often subjected to special acid and washing treatments to remove impurities therefrom before they can be used with the oil, which further increases their cost and prior to the present invention ave usually been discarded, after being used only once, because no satisfactory method has existed for recovering and reactivatin the used cla s without destroying their deco oriz-k ing or ltering value. 6o According to my invention it is possible to Y recover and restore the used clays to substantially to 9,0% of the decolorizing value o f the original clay and to repeat the restoratlon steps tento twenty times before the efb' 65 ciency of the clay falls so low as to make further revivication unproitable. i

The reviviied clay does not need'further .acid treatment and can be re-used for decolorizing oil substantially as well as new clay.

Previous attempts "to recover and reactivate filtering and bleaching clays used in contact filtration have been unsuccessful largely because of the failure to thoroughly remove the oil or naphtha from the vious to the burning of the clay so that the oil or naphtha became ignited and burned in the clay thus locally raising its temperature above the point of reactivation and destroying the value of the clay through overso urmng.

' It is the keynote of my present process that the hydrocarbons, oil andnaphtha are preliminarily removed so as to prevent any combustion in the' clay when it isgsubjeeted to a 85 higher reactivating temperature and that the higher reactivating temperature is carefully Y controlled to prevent overburning of the clay.

j, 'In my present process, I also recover` a lar e percentagefof the oil which is nory ma ly retainedin previously discarded clays and also recover the naphtha and substantially all of the clay which can then be economically reprocfessed and reintroduced into the system.

In the practice of my invention, the filter cake consistin of clay, sludge, and retained oil, is removec from the primary lter press 10 shown in Figure 1, in which the oil which passesout through the conduit 9 is separated 1C@ Y clay pre- 75 from the cl'a used in the decolorizing treatment. The lter cake which is contaminated with oil, slud e and impurities, is conducted by means of t e conduit 12 to the Wash tanks 14 which may preferabl be used 1n pairs and a suitable supply o naphtha is introduced into the wash tanks 14 by the conduit 16 and circulated with the clay y the pumps 18 to thoroughly leach out the oil contained in the cake. The mixture of oil, naphtha, and clay is then drawn from the wash tanks 14 through the conduit 20 by the circulating pump 22 which normally directs the mixture into the secondary ii ter press 24 by the conduit 26, the valve 28 in the conduit 20 being normally closed. The ilter cake from the first filter which has been suitably leached with naphtha to remove the entrapped oil is again pressed in the secondary filter 24 which may be of the continuous pressure type. To avoid the loss of volatile uids and reduce the fire hazard the oil and naphtha filtrate from this second filter 24 is removed through the conduit 32 and ydistilled in a suitable still to separate and recover the naphtha and oil.

The clay after leaving the secondary press 24 as filter cake, still contains a large amount of naphtha Which would become ignited and cause irregular burning-and destruction of the activity of the clay if subjected directly to a high heat. The clay is, therefore, first subjected to a mild heat in the clay drier 34 upon removal from the clay hopper of the secondary press 24. The clay drier 34 is preferably a cylindrical rotating drum tightly enclosed in the casing 34 and equipped with revolving arms scraping the sides of the cylindrical vessel and adapted to move the clay from the entrance to the outlet at a predetermined speed. The entrance and outlet of the drier 34 are properly sealed to prevent ignition of the naphtha vapors and the heat is regulated to drive off the naphtha Without igniting the same. The drier may be heated by any suitable means as by gas or fuel oil or flue gases or superheated stem. The heat of the drier 34 preferably should not exceed 450 to 500 degrecs F. which is sufficient to drive off the naphtha contained in the clay in a reasonably short time without igniting the naphtha vaors. p A vapor outlet 36 is provided on the drier to conduct the naphtha vapors to a condenser 38 rwhere they are collected and made ready for use again as solution naphtha.

A dust collector or screen may be provided at the outlet of the vapor conduit 36 to catch any fine particles of clay which might be mechanically carried ofi' with the vapors and the drier is also properly sealed at the inlet to prevent loss of fine clay.

The dried clay Which contains no naphtha and very little moisture, oil and impurities, is then discharged through the conduit 40 into the storage bin 42 from which the clay is then conveyed into the clay furnace 44 for further burning which is carried on at a temperature which may vary from 750 to 1200 degrees F. but preferably does not eX- ceed 875 to 900 degrees F. as temperatures in excess of this may bring about a structural change in the clay which destroys its absorbing and decolorizino' properties and makes it unsuitable for further use. It is desirable that a regular feed be maintained in proportion to the size of the furnace and the number of hearths in order to uniformly reactivate the clay and steam may be injected during this operation to produce slow regular burning of the clay. It is thus obvious that the small percentage of moisture Which remains in the cake from the clay drier is not an impediment.

The burned clay from the furnace 44 is dropped to the hopper 46 and finally stored in the finished clay storage tank 48 ready for re-use. This restored clay has about to 90% of the efficiency of new clay and it is not necessary in re-using it to again treat it with sulphuric acid. It can be used either as a dry clay or pulped with Water, thus saving the expense of the original acid treatment and pulping process. The restoration treatment may be repeated sometimes as high as twenty-two times before the efficiency o the clay drops gradually to 50 percent of the original.

By the present process, it is not only possible to recover substantially all of the naphtha used in the leaching step, but also to recover a very large portion of the lubricating stock which Was contained in the naphtha Wash and in the clay.

The preliminary separation of the naphtha from the clay in the drier 34 is a highly important step in the process as it not only permits recovery of the naphtha but prevents overheating and destruction of the clay in the further burning step.

Revivication of the clays necessitates burning or calcining of the clay at a temperature of 875 to 900o F. but higher temperatures may cause overburning and destruction of the decolorizing value. Previous attempts to reactivate bleaching clays, have neglected to remove the naphtha and oil from the cla s with theTesult that when subjected to high r temperatures the naphtha and oil in the clay caught fire and raised the calcining temperature and substantially destroyed the decolorizing value of the clay.

It is possible to construct a clay drier which Will remove a higher naphtha content (from seventy to eighty percent) from the filter cake after it has been in the Wash tanks 14 and it may therefore be unnecessary to use the secondary filter 24. If it is found that it is unnecessary because of the nature of the Washing treatment to use the secondary filter, it is only necessary to close the not absolutely valve 49 in the conduit `26 and the Valve 5() and below the clay hopper and open the valve 28 in the conduit 20 and the leached clay containing the high percentage of naphtha can be sent to the drier directly. The heat in the drier will thus cause a volatili'zation of the naphtha which will be condensed and recovered in the condenser coils 38 and the dried clay passed on directly to the clay'7 furnace 44 through 1 the storage bin 42. The secondary press is usually desirable but is economy of t e process and the rapidity with which the clay is to be treated may make it,

desirable to temporarily close off the second.- ary press.

A slightly modified form of the process for the treatment. of lubricating oil which has been heretofore acid treated is shown in Figure 2. Such oil which usually contains traces of free acid and sludge from such previous treatment cannot be steamed in the primary lter press due to corrosive and dev structive action by weakaoids produced by condensation of steam and the acid contained in the oil. Y

In this form of the apparatus the oil passes through the oil inlet 5l into the primary press 52 and the filtrate which is suitably treated and clarified lubricating oil stock passes outV of the filter through the outlet 53. As in the previous Aapparatus the filter' cake 'which is the clay to bey treated passes vthrough vthe conduit 54 into the wash tanks 55k and the naphtha forA leaching enters through the pipe' 56. The circulating pumps 57 recirculate the i mixture throughout the washtanks and finally discharge by `the aid of the'v circulating i pump 58 directly into rthe secondary press 59. Steam enters the secondary press through A' the conduit 66and it may be possible to eliminate suiiicient wash naphtha in this secondary press by steaming sothat the clay will become dry enough to drop from the lter surface and not contain enough naphtha to cause irregular burning in the recovery furnace. When this occurs, the dried filter cake drops into the conveyor 61 and is conveyed into -a steamed clay storage tank 62 from which it passes through the clay furnace 63 which is maintained at substantially the same temperature as the clay furnace 44 and suiicient to reactivate the clay for further use. The reactivated clay then drops to the burned clay hopper 64 and is finally stored in the/storage tank 65. Y

Due to the steaming in the secondary press,

a high percentage of naphtha isvdriven ol into the condenser 66'and`the water is separated from the naphtha ilr the water separator 67. After being condensed, the naphtha may be. drained ofi' to asuitable reservoir not shown, as suitable naphtha for re-use in Washing or it may be re-used in any other manner. Under certain conditions the clay essential and in some cases the `120 detected in the steam.

oil mixture which is introduced through the conduit 51 to the primary press 52 could be filtered and. washed Jin the press itself Arather than in separa-tewash tanks as heretofore discussed. The contact `filtering of `the clay oil mixture would be carried out as in normal operation and when the point is reached that it is no longer economical to continue the filtering cycle, the press may be washed withv warm naphtha introduced through the conduit .56` at a temperature of l to. I150 Ff. This washing is continued until the filtrate has reached a uniform color. A special narrow cut naphtha of high initial boiling pointis necessary for this Washing operation and it requires from five to twelve minutes. This reduces the oil contentof the cake to `below 2% and the `cake now contains f i' less than 2% oil and from, 35% to 40% nahtha.

pen steam is then introduced into thev press andl is allowed tosteam into a suitable v condenser which condenses the naphtha which is driven from vthe cake. The steaming op-v eration is continued until no naphtha can be This requires from vlive to fifteen minutesand .the cake then contains less than-1%,oil and-1% naphtha. Such a small amount of'napfhthazis unobjectionable in the revivifying yprc irregular burning.' 'p u' The cake lis then' fdropp convenient locations inside of tlie", press lso that the entire s'l'irface"ofn'they leaf jwill bev 1.00,

sprayed with high pressure;ls`team. 1 VThis thoroughly cleans theflfeafflldpr ents plugs...- n hendirectly conveyed into the closedstorag'ebins.62.where ging ofthesscr'een; "The clay iisA it-is stored preparato specialfurnaces 'In such a process, use the Wash tanks as the iltering and washing may be done directly on the filter and in the 4filter casing. It 1s also unnecessary to use the secondary press or the drier as fitoj burning.v in the the special solution naphtha is suiiicient' to reduce the oil `content and the steaming inthe filter will driveoii' the undesirable high naphtha content.

v'it jis not neces-sary to and will :not 'cause'05 y e fffhefleales, of the Pressby means of steam jets placedvgt:

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" It will thus `be obvious that this process 'per .be carried out in a mixing tank afterebeing .p discharged from the filter-so thatcontinuous v washing. of certain.y oils may be carried out in the filter press v steam the clays that j, have a tendency to sludge 'by using a filterp surface made of a compressed material such lfilters may be used or itself. It is possible to ascotton fiber or asbestos. It is also possible to recover a large percentage of the excessive fine material which runs through the filters in successive use and harms the our test and: emulsion test of the finished oil as well as machinery through which the oil comes in mits the ,use of any lterand washing'mayv i irc I' contact in successive operation-s. particularly possible when the washing is not carried on in the primary filter but in a separate wash tank, and after the washing and repulping, the cake is again filtered.

While I have described my process and shown preferred forms of embodiment thereof in connection principally with decolorizing clays, I am aware that other filter clays and modifications may be used and I therefore desire a broad interpretation of my invention within the scope and spirit of' the disclosure and of the claims appended hereinafter.

I claim:

1. The method of recovering and reactivating bleaching drocarbon oil and diluents therein, which comprises the steps of removing the clay from the primary filter, leaching the clay with a low boiling point hydrocarbon in separate wash tanks to recover the entrapped oil therefrom, refiltering the clay pulp to remove the leached oil and the low boiling point hydrocarbon, preliminarily drying the clay at a temperature below the ignition point of the low boiling point hydrocarbon to remove the low boiling point hydrocarbon without igniting the same, and finally subjecting the clay to a heat sufficient to revive the clay and higher than the flash point of the low boiling point hydrocarbon.

2. The process of recovering and reactivating bleaching clays for oil filtration which comprises removing the clay from the primary filter, washing and leaching the cake from the primary filter with naphtha to recover the entrapped oil therefrom, refiltering the Wash clay in the second filter, drying the clay in a drier maintained at a temperature between the volatilization point and the ignition point of the naphtha and the subsequent burning o the clay at a temperature not less than the temperature in the first Jfurthan necessary to reactinace and not more destroying its decolorvate the clay Without izing value.

3. The process according to claim 2 in which air is excluded from said first drier.

4. The method ing bleaching clays for use in the contact filtration of oils which comprises removing the clay from the primary filter press, washing the used clay with naphtha to free it from oil, removing the naphtha from the washed clay, preliminarily heating the Washed clay at a temperature below 500 F. to drive off the naphtha without igniting the naphtha vapors, and subsequently burning the clay to at approximately 800 to 900 F. to/remove organic materials and restore its bleaching activity.

5. The method of reactivating bleaching clay used in oil filtration which comprises removing the 'clay filter cake from the primary ilter press, washing said clay to reclays having absorbed hy- K of recovering and reactivat- This is move the entrapped oil therefrom, iiltering the washed'cla7 1n a secondary filter press tr,- separat'e the c ay from the washing liquid. preliminarily drying the clay to remove the Washlng liquid therefrom without igniting said washing liquid, and subsequently burning said clay at a heat suflicient to revivify the same.

In testimony whereof I have affixed my signature to this specification.

ERWIN R. LEDERER. 

